It's photoshop's internal version of a "file manager." Like a thumbnail viewer. One of the many things you can do within it is to encode things into the file, like who made it, when, where, with what. If it's a photo, you can add all you camera settings and descriptions etc. If you have an original picture of any of the Lost promo pics, you can view the info and find out Mario Perez took the picture, when he took it, where, what time, what camera he used (Canon EOS 20) and what the settings are. Also the episode name, date, time. All sorts of things. And you can open pictures right from Bridge into PS and back. It's fabulous.